The present invention relates in general to integrated monitoring systems, and more particularly to systems and methods for encapsulating a sensing element. The present invention is particularly useful for producing low cost optical sensor packages as well as multi sensor systems for the automotive industry.
Radiation sensing systems including integrated radiation sensors and often radiation transmission elements have become more widespread in their use in detecting position, rotation and fluid levels by optical means. While having the inherent drawback of requiring avoidance of any susceptibility to dirt, optical sensors impose no load on the sensed device or material. Optical sensors, including those using IR instead of visible light, often include a transmitter as well as a receiver to ensure the light levels are sufficient for accurate detection of reflected light from the target. Integrating the transmitter and the receiver into a single package has considerable cost benefits. In addition optical set up operations or tolerances can be reduced or eliminated since the combined package is manufactured and tested in a pre-aligned form.
Combining an IR radiation sensor in the same package as a pressure sensor in, for example, an automotive tire pressure sensor module can supply additional information concerning the temperature of the tire to the vehicle ECU""s for driver information or safety systems.
It is desirable to provide low cost integrated sensors, such as radiation sensors and pressure sensors, and efficient methods of producing the same.
The present invention provides integrated sensor packages for use in detecting radiation, e.g., visible and IR radiation, pressure and/or any other detectable physical property, and methods for producing the same. The techniques of the present invention include assembly methodologies that provide low cost sensor devices while maintaining the inherent high reliability as typically found in modern semiconductor packaging techniques.
According to the present invention, the elements of a sensor system are encapsulated into a single package. For example, elements of a wheel mounted tire pressure monitoring and transmitting system are encapsulated into a single package. As another example, elements of an optical transmission and detection system are encapsulated into a single package. The device elements are covered with a flexible gel coat and then inserted into a molding tool cavity. Each element may be individually coated with a separate gel blob, or all elements may be coated with a single gel blob. One or more retractable pins are incorporated into the molding tool and in their normal position are each in contact with the gel. A molding compound is injected into the cavity so as to encapsulate the device and gel coat. When the pins are extracted and the device ejected from the molding cavity, one or more passageways in the molding are left defined by the pins. The passageways expose the flexible gel covering the device elements to the atmosphere. For pressure sensitive elements, the gel, being flexible, transfers the local air pressure to the pressure sensitive element. For optical elements, the exposed gel is preferably removed to allow for the passage of radiation to and from the device elements, i.e., so as to define apertures. Alternatively, or additionally, an optically transmitting gel is used so as to allow for the passage of radiation at specific wavelengths.
According to an aspect of the present invention, a method is provided for encapsulating an integrated circuit device within a plastic molded package. The method typically includes providing an integrated circuit, the integrated circuit including a sensing element, applying a quantity of gel to the integrated circuit such as to cover at least the sensing element, thereby forming a gel-covered assembly, and inserting the gel-covered assembly into a cavity of a molding tool. The method also typically includes attaching a retractable pin to the gel-covered assembly, introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin, and removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the atmosphere through the passageway.
According to another aspect of the present invention, an encapsulated integrated circuit device is provided. The encapsulated device is typically formed, in part, by providing an integrated circuit, the integrated circuit including a sensing element, applying a quantity of gel to the integrated circuit such as to cover at least the sensing element, thereby forming a gel-covered assembly, and inserting the gel-covered assembly into a cavity of a molding tool. The encapsulated device is further typically formed by attaching a retractable pin to the gel-covered assembly, introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of the pin, and removing the pin from the gel such as to leave a passageway in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the atmosphere through the passageway.
According to yet another aspect of the present invention, a method is provided for encapsulating an integrated circuit device within a plastic molded package. The method typically includes providing an integrated circuit, the integrated circuit including a radiation sensing element and a radiation transmission element, applying a gel to the integrated circuit such as to cover at least the radiation sensing element and the radiation transmission element, thereby forming a gel-covered assembly, and inserting the gel-covered assembly into a cavity of a molding tool. The method also typically includes attaching at least two retractable pins to the gel-covered assembly, a first pin contacting the gel proximal the optical sensing element and a second pin contacting the gel proximal the optical transmission element, introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of each pin, and removing the first and second pins from the gel such as to leave passageways in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the atmosphere through the passageways.
According to a further aspect of the present invention, an encapsulated integrated circuit device is provided. The encapsulated device is typically formed, in part, by providing an integrated circuit, the integrated circuit including a radiation sensing element and a radiation transmission element, applying a gel to the integrated circuit such as to cover at least the radiation sensing element and the radiation transmission element, thereby forming a gel-covered assembly, and inserting the gel-covered assembly into a cavity of a molding tool. The encapsulated device is further typically formed by attaching at least two retractable pins to the gel-covered assembly, a first pin contacting the gel proximal the optical sensing element and a second pin contacting the gel proximal the optical transmission element, introducing a plastic mold compound into the cavity so as to encapsulate the gel-covered assembly and at least a portion of each pin, and removing the first and second pins from the gel such as to leave passageways in the plastic mold encapsulating the gel-covered assembly, thereby exposing the gel to the atmosphere through the passageways.
Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention. Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.